This invention relates to electron beam generating systems and, more particularly, to a novel and improved means for producing magnetic deflection fields to deflect the electron beam to material to be heated and to effect periodic deflection of the focal spot of the beam on the material.
An electron beam source serving for the treatment of material, such as melting, evaporating, welding, etc., comprises substantially a cathode emitting the beam electrons, a focusing electrode and an anode. With such a system, there can be generated a more or less focused electron beam of variable intensity. In order to guide the electron beam to the workpiece to be treated, means for producing suitable electrostatic or magnetic fields are arranged downstream of the beam generating system, where the electron beam undergoes the desired change of direction when it passes through these means.
It has been found that it is, as a rule, advantageous for electron beam-processing machines to use only magnetic deflection fields, in order to avoid troubles, such as caused by the necessary high control voltages and because of the insulation problems on electrostatic deflection elements. Magnetic deflection fields of variable intensity can be produced, as is known, by current carrying coils or windings, which have the disadvantage however, that they require considerable space and that they are not suitable for a low frequency beam deflection, because of their impedance, or that they require an undesired high operating voltage for higher frequencies.